Tris (2,3-dibromopropyl) phosphate (Tris) and tris (1,3-dichloroisopropyl) phosphate (Fyrol FR-2) have been studied in the male rat following iv., oral and dermal administration. Each of these compounds is absorbed from the gastrointestinal tract. Following absorption or iv injection these compounds are rapidly metabolized and excreted. The major metabolites are dealkylation products which are excreted primarily in the urine with lesser amounts being excreted in the feces or metabolized to CO2 and exhaled. In vitro studies have demonstrated that metabolism is mediated by both the microsomal mixed function oxidases and a soluble glutathione-S-transferase. A study of covalent binding to subcellular macromolecules has demonstrated that Tris has a greater affinity for DNA than does Fyrol and that this difference is most pronounced in the kidney.